The present invention relates to a rolling apparatus having a rolling member composed of a metallic rolling element and a metallic race element, at least one of the rolling element and the race element having been subjected to surface treatment for improving resistance to seizure and wear. More particularly, it relates to an improvement on lubricity in rolling apparatus, such as rolling bearings, linear guide apparatus, and ball screw apparatus.
Lubrication of the above-mentioned rolling apparatus having a rolling member is achieved with lubricants, such as oil and grease. The lubricant serves to form an oil film on the surfaces of the metallic rolling apparatus in contact with each other thereby to reduce the friction on the contact surfaces and to improve wear resistance. Under boundary lubrication in which a lubricating film may possibly be broken, and metal surfaces can come into direct contact with each other to cause solid friction or mixed friction, an extreme pressure additive for improving resistance to wear and seizure is added to the lubricant to prevent seizure and friction between metal surfaces.
However, lubricants such as lubricating oil and grease reduce their viscosity and consistency as temperature elevates as is expressed in terms of viscosity index. Therefore, as temperature increases, the film-forming function of the lubricant is reduced, and it follows that the contact surfaces of the metallic rolling member of a rolling apparatus come into the state of boundary lubrication. Under boundary lubrication, the extreme pressure additive added to the lubricant acts to prevent seizure through its chemical reaction. The problem in this case is that the non-seizure effect as expected cannot be obtained unless there is an outer factor (e.g., heat) inducing the chemical reaction between the extreme pressure additive and the metal surface.
The present invention has been completed taking a note of the above-described problem of lubrication associated with conventional rolling apparatus. Accordingly, an object of the present invention is to provide a rolling apparatus having a surface-treated rolling member exhibiting improved resistance against seizure and wear, in which an extreme pressure reaction film is previously formed on the metal surface to improve the wettability of the metal surface by a lubricant, and the wetting is maintained while running.
In order to accomplish the above object, the present invention provides a rolling apparatus having a surface-treated rolling member composed of a metallic rolling element and a metallic race element which have been used with a lubricant, in which the surface of at least one of the rolling element and the race element has a film comprising a compound produced by the reaction between the metallic component of the rolling element or the race element therefor and at least one compound selected from the group consisting of a phosphorus compound, a sulfur compound, a halogen compound, and an organometallic compound (the film will hereinafter be referred to as xe2x80x9creaction product subsurface layerxe2x80x9d), and a lubricant (oil or grease) containing at least one compound selected from the group consisting of an organic phosphorus compound, an organic sulfur compound, an organic halogen compound, and an organometallic compound as an extreme pressure component is present between the metallic contact surfaces of the rolling member.